Reptilase, also called haemocoagulase, is a novel haemostat drug with clinical application in recent years. It is an enzymatic haemostat isolated from the venom of fer-de-lance (Bothrops Atrox) and contains two active ingredients, batroxobin and clauden (a phospholipid-depending Factor X Acitivator). Batroxobin in reptilase stimulates the degradation of fibrinogen into fibinopeptide A and increased number of defibrination monomers which could linked to form fibrin I multimers. Haemocoagulase has an effect on the process of the cross-linked fibrin formation by fibrin I multimers, which results in the function of hemostasis. The fibrin I multimer can also stimulate platelet aggregation around vascular lesions and accelerate the formation of platelet tampon, thereby accelerating the effect of hemostasis at the site of vascular lesions. Clauden in reptilase can activate the Blood coagulation factor X which were concentrating on the surface of phospholipid reaction and then convert it into blood coagulation factor Xa. Factor Xa could then form a complex prothrombin activator together with calcium ion, blood coagulation factor Va and platelet phospholipid (PF3). This complex prothrombin activator catalyzes conversion of prothrombin to thrombin at the vascular lesions, thereby promoting the formation of blood clotting and thrombus. Reptilase does not induce blood clotting of the blood vessels with a usual dose. It has the effect of hemostasis only under the condition of bleeding, and it shows good therapeutic effect during the clinical application.
There are abundant research resources on snake venom in China. It has been reported that a special haemocoagulase with hemostasis effect can be isolated and purified from the snake venom of Agkistrodon acutus in China. However, due to the complicated components in the snake venom, there are two disadvantages of the biochemical venom products obtained by biochemical process: a) the whole operation is costly and difficult, b) other residue components after the process of purification may lead to different therapeutic effects and toxic side effects.
Therefore, genetic engineering was introduced into the study of batroxobin. The first application was in 1991. cDNA of batroxobin was isolated from the cDNA library of B. atroxmoojeni by Maeda etc., and was cloned into the expression vector of E. coli by recombination. Fusion proteins were expressed in the form of inclusion, and part of natural activities was obtained by refolding. However, the expression of mature and functional protein of batroxobin was not detected. In terms of structure, most batroxobins are glycoproteins. The expressed product can not be glycosylated due to the limit of the E. coli expression system itself, that is, lacking the function of posttranslational processing of proteins which is very important to protein intrinsic property and its biological functions. In 1996, Ancrod, a batroxobin originating from agkistroclon rlzodoston, was successfully expressed in epidermal cells of mice by Geyei etc. It was the first time that batroxobin was expressed in mammalian cells. It also showed that the structure of glycosylation is closer to that of the natural enzyme. Subsequently, batroxobin genes were cloned into pichia yeast to obtain a secreted product, Gussurobin, which also showed a higher biological activity. Therefore, it is generally believed that the expression of batroxobin genes should be performed inside the eucaryotic expression system.